1. Field of the Invention
The present invention relates to a delay circuit for delaying a combination signal defined by a code signal having a predetermined pattern followed by an information signal carrying a required data with the code signal and information signal being repeated periodically.
2. Description of the Prior Art
An example of the combination signal as defined above is a video signal which comprises a burst signal as the code signal and color signal as the information signal, with the burst signal and color signal fitted in 1H period (about 64 microseconds) and repeated again and again.
In the field of television, it is often necessary to delay the video signal by 1H, and for this purpose, a delay circuit defined by an ultrasonic delay line employing a comb filter having a piezoelectric element deposited on a glass plate or defined by a CCD (charge coupled device) is known.
When the ultrasonic delay line is employed for the delay circuit, there are disadvantages such that the delayed signal loses its power greatly, that the cost of the ultrasonic delay line itself is very high, and that the size of the ultrasonic delay line itself is very large when compared with other electronic elements arranged in an IC (integrated circuit) chip, resulting in high space factor.
On the other hand, when the CCD is employed for the delay circuit, there are disadvantages such that the CCD requires a high grade clock pulse generator for generating drive clock pulses having less deviation, resulting in high manufacturing cost, that the CCD consumes a great amount of power when compared with other electronic elements, that the CCD has an undesirable high radiation, and that it requires many external applications.